1. Field of the Invention
The present invention relates to a backlight module, and more particularly, to a backlight module in which conductive clips or clamping pins of current adjustment devices are employed to hold electrodes of lamps.
2. Description of Related Art
With liquid crystal displays (LCDs) being increasingly widely used in applications in daily life, stability of the optical performance and light and low profile industrial design of the LCDs are becoming increasingly important. Cold cathode fluorescent lamps (CCFLs) are usually used as the backlight source of the LCD. As the size of the LCD is getting larger, the number of the lamps used is increased. Accordingly, a technology of using multiple paralleled lamps (e.g., the lamps are arranged in parallel with each other) has been developed.
However, due to variations inherent among the lamps and variations of leakage currents of the lamps due to difference in lamps arrangement, the current flowing through each lamp varies accordingly, causing non-uniform brightness of the LCD panel (i.e., it is darker in some area, but is brighter in some other area). Therefore, controlling the current balance among the lamps is critical in achieving good image quality of the LCD.
In addition, conventional LCDs usually include an inverter system disposed on the back bezel of a backlight module, resulting in a large size of the backlight module. However, to reduce cost and make the product thinner, the inverter system may be disposed on one side of the backlight module, or the number of printed circuit boards of the inverter system may be reduced, or the volume of components of the inverter system may be reduced. Therefore, configuration of the light source and inverter system is also critical in achieving good image quality of the LCD.
FIG. 1 illustrates a conventional backlight module. Referring to FIG. 1, the conventional backlight module 100 includes a plurality of straight lamps 110, a first circuit board 120, a plurality of transformer coils 102 and a second circuit board 130. Each lamp 110 includes two lamp electrodes 111 at two ends, respectively. The first circuit board 120 is disposed on the lamp electrodes at one side, and each lamp electrode 111 is electrically coupled to the first circuit board 120. In addition, transformer coils 102 are positioned on the first circuit board 120 to provide suitable drive voltage for driving the lamps 110. The second circuit board 130 is disposed on the lamp electrodes 111 at another side, and each lamp electrode 111 is electrically coupled to the second circuit board 130. It can be seen from the above description that the backlight module 100 has no mechanism to adjust luminance uniformity of the straight lamps 110, and includes many transformers, which is adverse to reducing of number and volume of the components on the circuit board.
FIG. 2 is a perspective view of another conventional backlight module. Referring to FIG. 2, the conventional backlight module 200 includes a reflective plate 240, a plurality of lamps 210, a first circuit board 220, and a second circuit board 230. The lamps 210 are disposed above the reflective plate 240 and each lamp 210 includes electrodes 211 at two ends. The first circuit board 220 and the second circuit board 230 are disposed on the two ends of the lamps 210, with the electrodes 211 of the lamps being electrically coupled to the first circuit board 220 and the second circuit board 230, respectively. At least one power supply terminal 221 is disposed on the first circuit board 220 and the second circuit board 230.
As described above, features of the two conventional backlight modules are similar, and neither of their configurations takes the method of controlling current uniformity of the lamps into account, which is disadvantageous in achieving high brightness uniformity and image quality of the LCD. Furthermore, the lamps are directly coupled to the circuit boards. In assembly, the lamps need to be coupled to the circuit boards by, for example, soldering. This may be a hindrance to simplifying the assembly process of the backlight module. In addition, poor connection may occur during the assembly of the backlight module, which affects the yield rate and finally results in a rise of the manufacturing cost.